The invention described herein relates to a process and an apparatus for preventing the deposition of solid matter on the walls of tubular reactors.
Tubular reactors are well known and widely used in the chemical process industries. Almost as well known is their tendency to become fouled by deposits of solid material, necessitating frequent removal from service for a cleaning operation. Examples of processes subject to fouling include polymerization reactions, hydrocarbon cracking, and in general, any high temperature reaction involving hydrocarbons in which elemental carbon may be formed.
When reactor walls do become coated with deposits, a great number of difficulties ensue: (i) the heat transfer rate between the tube wall and the material in the centre of the tube diminishes; (ii) temperature regulation deteriorates, lowering control over the reaction and lessening the formation of the desired product and/or increasing the formation of unwanted side products, (iii) overheating often develops in the tubing, leading to shortened reactor life; (iv) frequent shut-downs and cleaning cycles are necessary, and the longer the reactor tubing, the more expensive and difficult the cleaning job; (v) damage to the reactor or ancillary equipment ensues when reactor tubes become plugged and relief valves burst; all of the foregoing difficulties may impair the safety of the entire reactor operation. Furthermore, these problems are aggravated by a need for long residence time and/or high treating temperature, as in the case of cracking operations.
When deposits have formed on the inside of reactor tubing, they may be removed by mechanical means (e.g., high pressure water or steam jets), by solvents (e.g., silane or hot hydrocarbons) or by chemical reaction (e.g., oxidation and/or reduction). However, all of these procedures require removing part or all of the reactor from service for the cleaning cycle.